// Initialize the sentinels.
public LinkedListQueue()
{
TopSentinel = new QueueCell <T>();
BottomSentinel = new QueueCell <T>();
TopSentinel.Next = BottomSentinel;
BottomSentinel.Prev = TopSentinel;
}
// Show the queue's values.
private void ShowQueue()
{
itemsListBox.Items.Clear();
for (QueueCell <string> cell = TheQueue.TopSentinel.Next;
cell != TheQueue.BottomSentinel; cell = cell.Next)
{
itemsListBox.Items.Add(cell.Value);
}
}
// Remove the target item from the linked list.
private void RemoveCell(QueueCell <T> target)
{
// Get the involved cells.
QueueCell <T> before = target.Prev;
QueueCell <T> after = target.Next;
// Reroute around the target cell.
before.Next = after;
after.Prev = before;
}
// Remove the oldest item from the queue.
public T Dequeue()
{
if (TopSentinel.Next == BottomSentinel)
{
throw new Exception("The queue is empty.");
}
QueueCell <T> target = BottomSentinel.Prev;
RemoveCell(target);
return(target.Value);
}
// Add an item to the queue.
public void Enqueue(T value)
{
QueueCell <T> newCell = new QueueCell <T>();
newCell.Value = value;
newCell.Next = TopSentinel.Next;
newCell.Next.Prev = newCell;
TopSentinel.Next = newCell;
newCell.Prev = TopSentinel;
}